Light emitting devices (LEDs) are compound semiconductor elements configured to convert electrical energy into light energy and may develop various colors by adjusting a composition ratio of a compound semiconductor.
Nitride semiconductor LEDs have advantages of low power consumption, semi-permanent lifetime, fast response speed, safety, and environmental friendliness when compared to conventional light sources such as fluorescent lamps and incandescent lamps. Accordingly, the nitride semiconductor LEDs are widely applied to light-emitting diode backlights that replace cold cathode fluorescent lamps (CCFLs) that constitute backlights of liquid crystal display (LCD) devices, white light-emitting diode lightings which can replace fluorescent or incandescent bulbs, vehicle headlights, and traffic lights.
However, white light using an LED has a problem of a low color rendering index (CRI). To solve this problem, there is a problem in that a phosphor configured to be excited in various wavelength bands has to be used.